# testing resisters

#### lorusso

Joined Nov 3, 2004
1
how do you test the resisters in a circuit and what is used

#### beenthere

Joined Apr 20, 2004
15,819
Hi,

You test resistors with an ohmmeter. Reading in circuit can give questionable results, as ther can be non-obvious conduction paths which will result in low readings. Always make sure the circuit is deenergized first. Having devices like ez-hooks rather than the normal probes makes life easier.

Learn the color code, too. It helps if you know in advance what the resistance should be.

#### Steel

Joined Oct 27, 2004
25
You will have to remove the resistor from the circuit. The ohm meter will also pick up other elements in the circuit.

If reading the color codes isn't good enough, then De-solder the resistor, remove it, and check the resistance with an ohmmeter.

#### sampinoy

Joined Sep 24, 2004
31
hello,

is there a way to check resistors without removing it from the board?

#### cyberhehe

Joined Oct 6, 2004
61
Originally posted by sampinoy@Nov 5 2004, 11:36 AM
hello,

is there a way to check resistors without removing it from the board?
[post=3356]Quoted post[/post]​

Yes there is, just pull out one leg then you dont have to remove it completely from the board haha, just kiddin. But you can do it this way for axial components. With chip resistors in surface mount implementation, you cnat do it this way

It will be very difficult to check the actual resistance of a resistor in circuit, specially if you dont know how it was connected within the schematic of the board. And even if you have schematic, it's difficult to do, i.e. you have a resistor to test that based on the schematic it is parallel with another resistor, though you may be able to analyze and get a calculated estimate on how much resistance you would expect to read including the surrounding component that may influence the reading.

Also another way you can do when doing some test in circuit, is to conduct voltage or current measurements. For transistor based circuits, voltage reading is very effective specially when checking the bias voltages from point to point. In this way, you can avoid doing resistance check by having some conclusions based on your voltage readings.